In order to develop new drugs for use in the treatment of behavioral disorders and central nervous system dysfunction, a battery of behavioral tests must be available for the assessment of the psychoactive properties of these substances. One behavioral paradigm that has been employed for this purpose has examined the effect of various pharmalogical agents on the self-administration of brain stimulation reward (BSR). In particular, this approach has proven useful in determining the addiction potential of drugs and in investigating the behavioral effects of anti-psychotic agents. However, the potential of this paradigm for characterizing the multitude of behavioral effects that might be produced by a drug has not been fully exploited. For example, although there is evidence that the effect of a drug on self-stimulation may depend on the joint effects of the stimulation site and response requirements, no systematic attempt has been made to explore this relationship. The proposed studies would examine the influence of response topography and differences in electrode placement on drug-induced changes in intracranial self-stimulation. Self-stimulation thresholds, response rates and response patterns will be assessed using a novel measurement strategy that manipulates brain stimulation train durations. Since little or no account is taken of differences in response topographies or stimulation site in most self-stimulation reserach, the results of the proposed studies may indicate that significant changes are needed in the methods currently used to assess the behavioral effects of pharmacological agents on BSR. They may also initiate a rethinking of how central reward and response control mechanisms jointly regulate goal directed behavior.